The present invention relates to a rocker system for push rod and overhead camshaft engines, more particularly to a variable compound rocker system having primary and secondary rocker assemblies adapted for varying valve lift.
Traditional push rod internal combustion engines include a single camshaft disposed in the valley of the engine block for actuating the intake and exhaust valves via pushrods and rockers that pivot about a rocker shaft. A disadvantage of this design, however, is that no convenient method for varying the lift of the intake valves exists. It is desirable to vary the lift of the intake valves to increase engine performance in certain applications. For example, during start-up it would be advantageous to lower the lift of the intake valves to help decrease fuel emissions and improve fuel economy. Similarly, at high cruising speeds it would be advantageous to increase the lift of the intake valves to increase performance. Hence, a rocker system capable of varying the lift of the intake valves in an internal combustion engine is desired. Such systems are disclosed in U.S. Pat. No. 5,560,329, U.S. Pat. No. 6,041,746, U.S. Pat. No. 6,055,949, and U.S. Pat. No. 6,123,053.
Each of these patents however, disclose or suggest a system of cams and linkages moving in sequence to vary the intake valve lift events. A disadvantage apparent to these configurations is the need for many moving parts, which increases the risk of failure. Another disadvantage of these systems is the loss of energy due to frictional and rotational resistances apparent in such complex configurations. A further disadvantage to these systems is the need for very particular assembly procedures, which lacks economic efficiency.
Thus, a simplified variable compound rocker system that is fully contained within the cylinder head is desired. This ensures compactness of the engine block, easy adaptation to current production push rod and overhead camshaft engines, and minimal energy losses due to friction and gyro dynamics.
The present invention provides a compound rocker system for varying the lift of intake valves adaptable for push rod and overhead camshaft internal combustion engines for use in motor vehicles. The rocker system includes a rocker shaft, a plurality of primary rockers positioned on a plurality of eccentric rings, a plurality of secondary rockers, and a plurality of exhaust rockers, all positioned on the rocker shaft. The primary rockers are adapted to actuate the secondary rockers, and the secondary rockers are adapted to actuate the intake valves. Furthermore, an actuator assembly is adapted to incrementally rotate the rocker shaft, thus changing the attitude of the primary rockers causing a variance in the lift of the intake valves. This allows for increased performance in different applications.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.